Rev. Hosp. Clin. vol.57 número4

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REV. HOSP. CLÍN. FAC. MED. S. PAULO 57(4):131-134, 2002 JULY-AUGUST

From the Study of Movements Laboratory of the Ortopaedics and Traumatology Institute, Hospital das Clínicas, Faculty of Medicine, University of São Paulo.

ORIGINAL ARTICLES

ISOKINETIC ASSESSMENT OF KNEE FLEXOR/

EXTENSOR MUSCULAR STRENGTH IN ELDERLY

WOMEN

Marcos de Amorim Aquino, Luiz Eugênio Garcez Leme, Marco Martins Amatuzzi, Júlia Maria D’Andréa Greve, Antônio Sérgio A.P. Terreri, Félix Ricardo Andrusaitis and Júlio César de Carvalho Nardelli

RHCFAP/3084 AQUINO M de A et al. - Isokinetic assessment of knee flexor/extensor muscular strength in elderly women. Rev. Hosp. Clín.

Fac. Med. S. Paulo 57(4):131-134, 2002.

OBJECTIVE: To assess knee flexor-extensor muscular strength in elderly women with no previous history of musculoskeletal disorders on the lower limbs using an isokinetic dynamometer, in order to obtain data that could be used as a comparative parameter in the evaluation of elderly women with knee disorders, thus facilitating a better rehabilitation of these patients.

METHODS: Twenty-six volunteers aged 75 to 83 years were studied using a Cybex®_{6000 isokinetic dynamometer.}

The chosen angular velocity was 60 º/s, and concentric exercise was used for either flexion or extension. The studied parameters were: peak torque, angle of peak torque, and flexor-extensor torque rate.

RESULTS: There were no differences between dominant (D) and nondominant (ND) knee peak torque values. This was true for both flexor (D = 42.46 ± 9.09 Nm / ND = 40.65 ± 9.38 Nm) and extensor (D = 76.92 ± 13.97 Nm / ND = 77.65 ± 15.21 Nm) movements. The descriptive statistical analysis of the values obtained for the flexor-extensor peak torque rate and for the angle of occurrence of peak torque was the same for the dominant and nondominant sides.

CONCLUSIONS: The values of peak torque for the contralateral side can be used as a reference during rehabilitation of elderly women with acute disease of the knee, and the angular velocity of 60 º/s is proper and safe for isokinetic assessment of elderly people.

DESCRIPTORS: Isokinetic. Knee. Torque. Muscular strength. Elderly.

INTRODUCTION

The elderly population is growing world-wide10_{. This epidemiological}

re-ality requires a deeper knowledge of their musculoskeletal systems1_{. Since}

muscular deficiency is a frequent cause of instability and unbalance, proper muscular assessment is important for preservation of joint stability and for preventing falls and disability6,9_.

Isokinetic assessment is the most accurate method for evaluation of mus-cular activity11_{. The measurement is}

made using a dynamometer with a

computerized system that permits arcs of movement at a constant angular ve-locity that has been determined previ-ously. Isokinetic assessment is used for the assessment of muscular equilib-rium and for rehabilitation of injuries7_.

However, there are only a few pub-lished studies about isokinetic

assess-ment for the flexor and extensor mus-cles of the knee in elderly people1,3_.

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METHODS

Twenty-six volunteer women aged 75 years or more with no musculoskel-etal disorders in lower limbs were stud-ied. They underwent a computerized isokinetic assessment of the flexor and extensor muscles of the knees using a CYBEX®_{6000 dynamometer. The}

study was approved by the local com-mittee, and informed consent was ob-tained from the volunteers before in-clusion.

The medium age was 77.85 ± 2.81 years, ranging from 75 to 83 years. Medium weight was 63.96 ± 10.12 kg, ranging from 48 to 100 kg, and me-dium height was 1.55 ± 0.06 m, rang-ing from 1.44 to 1.66 m. The dominant side, which was considered the prefer-able one for kicking by the volunteer7_,

was the right side for 88.46% of the volunteers.

Criteria used for the selection of the volunteers

The criteria used for the selection of volunteers in this study were: a) age = 75 years b) female; c) sedentary life-style (no more than 1 hour of physical activ-ity/week)2,3_{; d) no history of pain in any}

knee with limitation of the habitual ac-tivities for more than 48 hours during the last 2 years; e) no history of previous musculoskeletal disorders4,14_{; no nervous}

diseases or previous fractures in the lower limbs5_{; f) no instability in any planes or}

angular deviations in the knees (varus or valgus larger than 10 degrees)16_{; g) no}

use of a pharmacological substance that might affect the mechanism of muscular contraction14_{; h) no previous isokinetic}

assessment; i) no unbalancing systemic disease, such as cardiac diseases and hy-pertension.

Protocol used for the isokinetic assessment

The flexion and extension tests

were carried out using an angular ve-locity of 60 º/s. At least 5 minutes of exercise was performed on a flat mat with a walking speed that was previ-ously determined. In order to limit knee movement, the test was per-formed with the volunteer sitting, with the belts positioned on the thorax, ab-domen, thigh, and above the knee on the side that was being evaluated8_{. The}

force due to gravity was corrected for by an intrinsic device of the dynamometer5_{. Each volunteer}

ex-ecuted 4 valid repetitions for each test. In order to isolate the movements of the knee as much as possible, the vol-unteers were told not to hold on to the lateral supports during the test11,14_{. The}

tests were performed bilaterally, always beginning on the dominant side. The following parameters were evaluated: a) peak torque, in their absolute val-ues; b) angle of occurrence of peak torque; and c) flexor-extensor peak torque rate. All the values obtained corresponded to concentric contrac-tions.

Statistical analysis

The statistical analysis was per-formed using nonparametric tests. The comparison between the dominant side and the nondominant one was made using the Wilcoxon test. The level of significance used in every comparison was 5% (P = 0.05%).

RESULTS

There were no statistically signifi-cant differences between the values of peak torque and the angle of occur-rence of peak torque for the dominant and nondominant sides. This was true for both flexor and extensor move-ments (Tables 1 and 2). The descrip-tive statistical analysis of the values obtained for the flexor-extensor peak torque rate was the same for the domi-nant and nondomidomi-nant sides (Table 3). The values for peak torque corrected for corporal weight that were found in the isokinetic assessment followed the

Table 1 - Peak torque of the knee at 60 º/s (Nm).

Muscles Dominant side (n=26) Nondominant side (n=26)

aver. min-max SD aver. min-max SD

Flexor 42.46 28 - 60 9.09 40.65 26 - 58 9.38

Extensor 76.92 58 - 118 13.97 77.65 56 - 127 15.21

SD - Standard Desviation

Table 3 - Flexor-extensor relationship (%).

vELOCITY Dominant side (n=26) Nondominant side (n=26)

60 º/s 5 5 39 - 75 8.67 52.12 40 - 80 9.47

SD - Standard Desviation

Table 2 - Angle of peak torque of the knee at 60 º/s (°).

Muscles Dominant side (n=26) Nondominant side (n=26)

Flexor 31.46 20 - 46 7.23 31.54 17 - 47 8.58

Extensor 56.96 42 - 71 7.55 54.31 43 - 76 8

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same pattern of the absolute values obtained, so the inclusion of these corrected values in the analysis was not necessary.

DISCUSSION

We were challenged to determine the angular velocity that would be used in our study. We needed to find an angular velocity that would allow us to perform proper evaluation with-out risking the physical integrity of volunteers. We adopted the angular velocity of 60 º/s, because it is appro-priate for the assessment of peak torque in elderly people, and it is one of the safest angular velocities for the patellofemoral joint15_{. In addiction,}

using this angular velocity would al-low us to compare our results with other data in literature12,18_.

The results showed that there were no statistically significant differences be-tween the values of peak torque and of the angle of occurrence of peak torque for the dominant and nondominant sides. This was true for both flexor and exten-sor movements. These results were simi-lar to those reported for young women18

and are very important, since data in the literature show that peak torque is the best correlated measurement in isomet-ric exercise13_.

Therefore, the results allow us to use the values of peak torque of the non-affected side as the preferable ref-erence parameter during the rehabili-tation of elderly people who have ex-perienced trauma to the knee.

However, it is essential to empha-size that this comparison should not be extended to patients with chronic diseases on the knee. Since these dis-eases often occur bilaterally, it would be a mistake to assume that an injured contralateral lower limb is a measure of normality. The complaint of pain during isokinetic assessment for pa-tients with patellofemoral disease might result in an inappropriate evalu-ation of the real functional capacity of these patients, and consequently, in inappropriate rehabilitation programs. The descriptive statistical analysis of the values obtained for the flexor-extensor peak torque rate was the same on the dominant and nondominant sides. The extensor peak torque was almost the double that of the flexor peak torque. These results are similar to those reported in literature12_.

We had difficulty comparing the results obtained in our study with those in literature, since there are only a few available studies on isokinetic assessment of the flexor and extensor muscles of the knee among elderly

people1,3_{. There are even fewer studies}

on elderly women. The lack of a stand-ard angular velocity for this kind of assessment is a further problem, with evaluations obtained using many dif-ferent angular velocities, making any comparison between them unfeasible.

The knee joint, due to its anatomi-cal and functional characteristics, is one of the most mechanically over-loaded joints and the most unstable one in the musculoskeletal system, which makes it the most susceptible joint to lesions. The older the patient, the higher the frequency of this kind of dis-order. For this reason, we point out the need for obtaining data that could be used as a standard parameter for elderly women with disease of the knee, thus allowing for a proper follow-up and a better assessment of the degree of recov-ery in these patients in order to optimize the rehabilitation programs.

CONCLUSIONS

We concluded from our study that the values of peak torque for the non-affected side can be used as a reference during the rehabilitation of elderly women with acute disease of the knee and that the angular velocity of 60 º/s is proper and safe for isokinetic assess-ment among elderly people.

RESUMO RHCFAP/3084

AQUINO MA e col. – Avaliação isoci-nética do torque muscular flexor-extensor do joelho em mulheres com idade entre 75-83 anos. Rev. Hosp. Clín. Fac. Med. S. Paulo 57(4):131-134, 2002.

OBJETIVO: Avaliar, isocinetica-mente, o torque dos músculos flexores e extensores dos joelhos de mulheres idosas sem afecções do sistema mús-culo-esquelético em membros

inferio-res, obtendo dados que possam servir como parâmetro de comparação na avaliação de mulheres idosas portado-ras de afecções nos joelhos, colaboran-do para uma melhor reabilitação des-sas pacientes.

CASUÍSTICA E MÉTODOS: Vin-te e seis voluntárias foram avaliadas. O estudo foi realizado através de um dinamômetro isocinético marca CYBEXâ modelo 6000 na velocidade

angular de 60º/s. O tipo do exercício

utilizado foi o concêntrico, tanto para a flexão quanto para a extensão do jo-elho. Os parâmetros avaliados foram o torque máximo, o ângulo de ocorrên-cia do torque máximo e a relação flexão/extensão do torque máximo.

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9,09 Nm / ND= 40,65 ± 9,38 Nm), quanto para o movimento extensor (D= 76,92± 13,97 Nm / ND= 77,65 ± 15,21 Nm). Também, a estatística des-critiva dos valores encontrados para a relação flexão/extensão do torque má-ximo e para o ângulo de ocorrência do

torque máximo foram semelhantes nos dois lados avaliados.

CONCLUSÕES: Os valores do torque máximo do lado contralateral podem ser usados como referência du-rante a reabilitação de mulheres ido-sas portadoras de doença articular

agu-da no joelho e a velociagu-dade angular de 60º/s é adequada e segura para a ava-liação isocinética em idosas.

DESCRITORES: Isocinético. Joe-lho. Torque. Força muscular. Idoso.

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